Candles are popular, but they do pose risks due to fire and smoke. While scented wax melts that release aroma with out flames have been marketed as a safer option, new research indicates they also pose risks.
Authors of the new research conducted experiments on 15 commercially available wax melts in a full-scale model house. Their findings were published this month in the American Chemical Society’s Environmental Science & Technology Letters journal.
Researchers already knew that evidence indicated scented wax melts heated on a warmer emitted even more aroma than traditional candles, since the direct method of heating allowed more volatile organic compounds (VOCs) made of hydrocarbons into the air. Inside the model home, the established a baseline of indoor pollutants before switching on the wax warmer for around two hours at a time to test both unscented and scented wax melts.
“During and after this period, the researchers continuously sampled the air a few yards (meters) away from the wax melts and found airborne nanoparticles, between 1 and 100 nanometers wide, at levels that were comparable to previously reported levels for traditional, combustion-based candles,” said a press release about the study from the American Chemical Society (ACS).
Compounds released by melting the wax react with other compounds in the air to create nanometer-wide particles. According to the researchers, these particles are dangerous because they are small enough to potentially pass through respiratory tissues and enter the bloodstream if inhaled. They said the risk seemed to be linked to the scented wax melts.
“In the experiments, the main VOCs emitted from the wax melts were terpenes, such as monoterpenes and monoterpenoids. The researchers identified that the airborne terpenes reacted with ozone and formed sticky compounds, which aggregated into nanoscale particles,” the ACS explained. “However, after warming an unscented wax melt, the team observed no terpene emissions or nanoparticle formation, which suggests that these aroma compounds contribute to nanoparticle formation.”
Still, the study authors said their discoveries “challenges” the narrative that wax melts are a safer alternative to combustion-based candles. Per the National Candle Association, $3.14 billion candle products are sold each year in the U.S., and fragrance is by far the top characteristic consumers consider when purchasing these products. Candles were also identified as the cause of 4% of home fires, 3% of home fire deaths and 6% of home fire injuries from 2018 to 2022, according to the National Fire Protection Association.
Going forward, more toxicology research is needed to determine the risks of breathing in nanoparticles formed from wax melts, said the study authors. They previously conducted an analysis on how airborne nanoparticles form indoors from volatile scent compounds that was published in 2024 in ACS ES&T Air.